Bone fixation screw and method

ABSTRACT

A screw device for compressing and fixing together a proximal and distal bone part along a surgical axis comprising: a bone screw portion comprising an elongate body inscribed with bone screw threads at a leading end of an outer surface of said body; an elongate tubular torque stabilizer portion for spanning said bone parts and comprising one or more torsion stops to engage each bone part to limit rotational movement between the bone parts and a translation stop on said torque stabilizer to seat against a portion of the proximal bone to limit translation of said torque stabilizer portion along the surgical axis; and a compressor lock portion engaging the bone screw portion and torque stabilizer portion to draw said bone screw portion proximally along the surgical axis toward said translation stop therein compressing said one parts together.

The present application is a utility patent application that claimspriority to U.S. Provisional Application Ser. No. 61/650,440, filed onMay 22, 2012.

BACKGROUND

The present invention relates generally to the stabilization of adjacentbone portions and particularly for the stabilization of fractures. Hipfractures, for example, are a common problem that is often challengingto remedy. Femoral neck fractures of the hip typically involve thenarrow neck between the shaft of the femur and the round head. Thedevice disclosed may be used to secure and compress the bone segments oneach side of the fracture site.

SUMMARY OF THE INVENTION

Disclosed herein is a bone screw assembly for stabilizing andcompressing together two or more bone parts. In its preferred form thisassembly is well suited for stabilizing femoral neck fractures utilizinga minimal incision at the operational site.

In one form, the invention is directed to a bone screw fixation assemblycomprising a bone screw portion, a torque stabilizer portion, and acompressor lock portion. After placement of a guidewire, and boring withsurgical drills, the bone screw portion comprising distally placed bonescrew threads is fed over the guidewire and seated into the head of thefemur at a predetermined location. A tubular torque stabilizer portioncomprising a second positioner is advanced upon a first positioner onthe bone screw portion therein eliminating rotational motiontherebetween. Torsional stops projecting from the outer surface of thetorque stabilizer portion seat into the bone therein eliminating therotational motion between the bone and torque stabilizer and between adistal and proximal bone segment. A translation stop on an enlargedportion of the torque stabilizer abuts a portion of the proximal bonesegment once the stabilizer is fully seated.

A compressor lock portion advances on the proximal end of the bone screwportion therein causing compression forces on the bone between thetranslation stop and the bone screw therein fixating the bone portionstogether and preventing torsional motion therebetween.

In one form, torsional stops on the torque stabilizer portion extenduninterrupted from a proximal to a distal end.

In one form, the torque stabilizer portion is in the form of anelongated key.

In one form, the 2^(nd) positioner on the torque stabilizer portion iscaptured within the 1^(st) positioner on the bone screw portion.

In one form, the torque stabilizer portion comprises an integratedfixation plate configured for fixation on a lateral surface of thefemur.

In one form, the compressor lock is in the form of a screw that advanceson a proximal end of the bone screw portion. In another form, thecompressor lock is in the form of a cap nut that advances on a proximalend of the bone screw portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective exploded view of a preferred embodiment ofa bone fixation screw assembly.

FIG. 2 is a front perspective view of a bone screw portion.

FIG. 3 is a close-up view of the proximal end of the bone screw of FIG.2.

FIG. 4 is a front perspective view of the bone screw illustrated in FIG.2 from the distal end.

FIG. 5 is a side view of the bone screw illustrated in FIG. 2.

FIG. 6 is a distal end perspective view of a preferred embodiment of atorque stabilizer portion.

FIG. 7 is a proximal end perspective view of the torque stabilizerillustrated in FIG. 6.

FIG. 8 is a distal end view of the torque stabilizer illustrated in FIG.6.

FIG. 9 is a distal perspective view of another form of a torquestabilizer comprising a continuous torsion stop.

FIG. 10 is a distal end perspective view of a preferred embodiment of acompressor lock portion.

FIG. 11 is a proximal end perspective view of the compressor lockportion illustrated in FIG. 10.

FIG. 12 is a front perspective exploded view of another form of a bonefixation screw assembly utilizing an elongated key form of a torquestabilizer.

FIG. 13 is a proximal perspective view of the elongated key illustratedin FIG. 12.

FIG. 14 is a distal perspective view of an alternative form of acompressor lock illustrated in FIG. 12.

FIG. 15 is a proximal perspective view of the bone screw portionillustrated in FIG. 12.

FIG. 16 is an end view of the bone screw bone screw portion illustratedin FIG. 15.

FIG. 17 is a front perspective view of the bone fixation screw assemblyillustrated in FIG. 12 in its operational configuration.

FIG. 18 is a front perspective exploded view of another form of a bonefixation screw assembly comprising an integrated fixation plate.

FIG. 19 is a proximal perspective view of the torsional stabilizerportion of the bone fixation screw assembly illustrated in FIG. 18.

FIG. 20 is a front view illustration of the bone fixation screw assemblyof FIG. 18 in its operational configuration within a fractured femur.

FIG. 21 illustrates placement of a guidewire within the femoral head.

FIG. 22 illustrates the bore created by a surgical drill and advancementof the bone screw portion down the surgical path.

FIG. 23 illustrates the advancement of a bone screw portion to apredetermined location in the femoral head and advancement of the torquestabilizer portion through the bone so and over the shank of the bonescrew portion.

FIG. 24 illustrates the torque stabilizer portion fully seated over thebone screw portion with torsional stop limiting rotation between bonesegments.

FIG. 25 illustrates advancement of the compressor lock into the proximalend of the bone screw portion.

FIG. 26 illustrates a fully advanced compressor lock therein drawing thebone screw portion proximal therein closing the fracture gap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a preferred embodiment illustrated in FIG. 1, the fixation screwassembly 100 comprises a bone screw portion 200, a torque stabilizerportion 300, and a compressor lock portion 400. Although not necessary,it is preferred that one or more parts of the screw assembly 100 iscannulated to pass a guide wire for guidance of the assembly to apredetermined bone site location.

In the preferred embodiment of the device, the bone screw portion 200illustrated in FIGS. 2-5 comprises a cannulated elongate body 201 withcentral axis ‘A’. Positioned on the distal end 202 over the outersurface 203 of the elongate body 201 are several bone screw threads 204with a tapered lead-in 205. Proximal along the elongate body 201 fromthe threads 204 is a shank portion 206 of the bone screw 200 and acontinuation of the elongate body outer surface 203.

The bone screw threads in this embodiment are configured to seat withinthe softer cortical bone of the head of the femur. For this reason, thethreads may be deep and generously spaced for capture within this softerbone. For example only, the pitch may be about 8 threads per inch with aminor diameter of about 0.285 inches and a major diameter of about 0.470inches. These values may be adjusted accordingly to accommodate theindividual patient's bone density, skeletal stature, and otheroptimizing factors.

The bone screw portion 200 of this preferred embodiment is configured tobe driven into a pre-bored hole. Although not necessary, it is preferredthat the minor diameter of the screw threads 204, the diameter of theshank portion 206, and the drill diameter are of similar size. A drilldiameter that is too large will reduce the torque required to seat thebone screw portion at its predetermined location, but effectivelyreduces the amount of screw purchase by the threads therein reducingresistance to screw pullout. A drill diameter that is too small willincrease the torque required to drive and seat the bone screw portion.The screw threads may be configured with a sharp leading cutting tip 207for self-tapping the screw into the pre-drilled hole. Alternatively, theleading thread may have a softer lead-in typically configured for apre-tapped hole. The softer lead-in thread may also prove to be lessdamaging if the screw is mistakenly driven beyond the bone surface andinto nearby joint space since it will be less damaging to nearby softtissue. Similarly a soft thread lead-out 208 may ease removal of thebone screw portion for repositioning. A sharp lead-out 208 may be moreeffective when removal is required after osseointegration. A drillhaving a diameter slightly larger than the shank diameter may ease theforce required to later drive the torque stabilizer portion 300 over thebone screw portion.

A variety of thread profiles may be used. The thread faces, may beadapted to improve thread purchase. For example, the leading face 209 ofthe threads may stand generally perpendicular to the screw axis orsloped proximal or distal. Similarly, the trailing thread face 210 mayalso stand generally perpendicular to the screw axis or sloped proximalor distal. The thread thickness ‘T’ may be adjusted for a pre-determinedpurchase strength, thread strength, or to produce a desired frictionwhen driven into a pre-threaded or un-threaded hole. The threads at themajor diameter may be notched (not shown). Each portion of the deviceincluding the thread surface 211 and elongate body outer surface 203 maycomprise coatings such as hydroxyapatite, titanium oxides, osseospeed,osseotite, bio-tite or surface treatments such as blasting or etching toencourage osseointegration. These coatings or surface preparations canbe effective at stabilizing the implant in its predetermined position.Their necessity is lessened in this embodiment since the torquestabilizing portion 300 of the assembly comprises features to not onlystabilize the implant, but also stabilize position of one bone portionin relation to the other. This will be described in detail in laterparagraphs.

The bone screw portion 200, as illustrated in FIG. 2-5, comprises afirst positioner 212 and the torque stabilizer portion 300 comprises asecond positioner 301 illustrated in FIG. 8. These positioners cooperateto perform several functions. In this embodiment the first positioner212 is in the form of a linear rectangular groove 213 following thecentral axis ‘A’ and extending the entire length of the bone screwportion outer surface 203 including extending through the bone screwthreads 204. Although less preferred, the first positioner 212 couldstop before reaching the distal end 202 of the bone screw portion 200 oreven before reaching the threads of the bone screw portion.

The first positioner 212 may take forms or profiles other than a groove213 such as a ridge, notch, or one or more bumps. These first positionerfeatures serve to guide the torque stabilizer portion 300 to apredetermined position over the outer surface 203 of the bone screwportion 200 elongate body 201. Alternatively, the shank portion 206 maybe non-circular to serve the function of a positioner together with acomplementary profiled torque stabilizer portion.

The first positioner 212 in the preferred embodiment is in the form of agroove that serves several functions. As discussed previously, thisgroove 213 defines a predetermined path for the torque stabilizerportion 300 to follow as it is inserted. Second, the groove 213 preventsrotation between the torque stabilizer portion 300 and the bone screwportion 200. The third function is the grooves lateral walls 214 assistin stabilizing the distal torsion stops 309, FIG. 6, as they cut throughthe bone therein preventing the stops 309 from breaking or bending andkeeping them aligned along the cutting path for eased insertion as theycut through the bone.

Further in this embodiment, the first positioner groove 213 comprises abottom wall 215 spaced from the inner cannula wall 216 a pre-determineddistance ‘S’ to maximize depth of the wall 215 while maintainingsufficient strength of the elongate body 201.

The proximal end 222 of the bone screw portion 200 comprises drivesurfaces 218 illustrated in this preferred embodiment in the form ofopposing flat surface portions 219 inscribed into the elongate bodyouter surface 203. Alternatively the drive surfaces 218 could be on theproximal face 220 in the form of notches extending into the proximalface of the bone screw portion 200. As a further alternative, the drivefaces 218 could be integrated with the first positioner groove 213 thuseliminating the need for a separate set of drive surfaces.

At the proximal end 222 of the bone screw portion 200 is a fastenerportion 221 which may be in the form of ridges, grooves, notches,threads 223 or other feature suitable for attaching an instrument orother portions of the implant device such as a compressor lock 400. Inthe preferred embodiment the fastener portion 221 is in the form ofthreads 223 inscribed in an enlarged diameter portion of the innercannula surface 216 of the bone screw portion 200. The fastener threads223 extend partially down the cannulated opening but in alternativeembodiments may extend to the distal end 202. The fastener threads 223function to secure a bone screw insertion tool (not shown) to theproximal face 220 of the bone screw portion when driving and positioningthe bone screw portion 200 into the predetermined position within thefemoral head. As will be described later, the fastener threads 223 arelater utilized by the compressor lock 400 to draw closer the bone screwportion 200 and the torque stabilizer portion 300 of the bone fixationscrew assembly 100 therein compressing and thus stabilizing the fracturesite.

A preferred embodiment of the torque stabilizer portion 300 of the bonereduction screw assembly 100 is illustrated in FIGS. 6-8. The torquestabilizer 300 comprises an elongate tube body 304 defining an innersurface wall 305 sized to slide over the elongate body outer surface 203of the bone screw portion 200.

The outer surface 303 of the torque stabilizer 300 comprises one or moretorsion stops 302 or rotation resistors to limit rotational movementabout axis ‘B’ with respect to the surrounding bone. Two to four torsionstops at each end are preferred. The preferred embodiment comprisestorsion stops 302 near the proximal end 307 and near the distal end 306.As seen in FIG. 6, a proximal torsion stop 310 is located at theproximal end of the elongate tube body 304, and a distal torsion stop309 is located at the distal end of the elongate tube body 304 extendingfrom the tube body outer surface 303 and leading end surface 311 of theelongate tube body 304. Illustrated in FIG. 8, these stops 309 have awidth ‘W’ between opposing stop side walls 308 to slide with minimalfriction within the first positioner groove 213. The distal torsion stop309 also has an inner wall 312 spaced from the central axis a distance‘R’. This inner wall 312 defines the second positioner 301 that iscaptured within the first positioner groove 213. Distance ‘R’ is justenough to provide the elongate tube body 304 free movement along thebone screw portion 200.

The torsion stop 302 may be configured with cutters in the form ofsharpened edges 313 at the leading end and distal radial sides furthestfrom the central axis ‘B’ of the elongate tube body. The leading andtrailing edges of the torsion stops 302 may be tapered 314 to easecutting through bone.

The torque stabilizer portion 300 comprises a distal facing translationstop 315 near the proximal end 307 of the elongate tube body 304. Inthis embodiment, the translation stop 315 is in the form of an enlargedportion 321 of the elongate body outer surface defining a stop surfacefor abutting against bone in the pre-bored hole in the bone.

Again, the proximal end 307 of the torque stabilizer portion 300comprises one or more proximal torsion stops 310 serving to preventrotation of the torque stabilizer portion once it is fully secured intothe bone parts. In this preferred embodiment, the proximal torsion stops310 are in the form of fins 316 extending from the enlarged portion 321of the elongate body 304. The fins 316 comprise a lead wall 317, atrailing wall 318, side walls 319, and a distal radial wall 320. Theside walls 319 may be inclined to define a sharper distal radial wall320 edge. The leading edge 317 or trailing edge 318 of the fins 316 maybe tapered and the leading edge may be sharpened to ease insertion intothe bone. The leading edge surface of the torque stabilizer portion mayalso be sharpened for the same purpose.

The elongate body 304 of the torque stabilizer 300 in the operationalconfiguration spans the bone segments. The proximal torsion stops 310 atthe proximal end and the distal torsion stops 309 at the distal end ofthe torque stabilizer function to engage each bone part. Alternatively,the one or more continuous torsion stops 322 could be extended along theelongate body of the torque stabilizer a distance effective to span bothbone segments as illustrated in FIG. 9. This modification wouldeliminate the need for having both proximal and distal stops 310, 309.

A fastener portion 323 illustrated here in the form of threads 324 isinscribed in the inner cannula surface 305 of the torque stabilizerportion 300 in the preferred embodiment. The fastener threads 324 extendpartially down the proximal cannula opening and functions to secure atorque stabilizer insertion tool (not shown) to the proximal face 325 ofthe torque stabilizer portion 300 for driving and positioning the torquestabilizer portion into the predetermined position within the femoralneck and head. The proximal face 325 of the torque stabilizer portion300 may include a taper to minimize portions of the implant fromprotruding above the bone surface.

The preferred embodiment of the bone fixation screw 100 assemblycomprises a compressor lock 400 in the form of a screw. The screw 401 asillustrated in FIGS. 10-11 comprises a head 402 and a shaft 403. Theshaft 403 includes a lead face 411, threads 404 and is configured tocooperate with the threads 223 inscribed in the inner cannula surface ofthe bone screw portion 200. Rotation of the screw 401 will advance theshaft 403 down the threaded cannula of the bone screw portion. Facingdistal 412 on the underside of the screw is a reduction surface 405 usedto abut the proximal face 325 of the torque stabilizer portion 300therein approximating the bone screw portion 400 and torque stabilizerportions 300 together to effectively compress the fracture as thecompressor lock 400 is advanced.

The compressor lock 400 comprises a drive 406, here in the form of oneor more drive pockets 407 formed in the head 402 of the screw 401. Thedrive pocket 407 comprises 2 or more drive surfaces 408 to abutcomplementing drive surfaces on a screw driver tool used to transmittorque from the user to the screw. Alternatively, the drive surfaces 408may be formed on the radial wall 409 of the screw head 402 or on anextension from the screw head. It is preferred that the head of thescrew is smooth to prevent irritation to the surrounding soft tissue.

The compressor lock 400 may further comprise an anti-backout feature.For example, the reduction surface 405 on the screw and the proximalsurface 325 of the torque stabilizer portion 300 may be configured withinterlocking splines 410 that would require overcoming the frictioncreated between the splines before the screw can begin to back out. Thelock 400 may also comprise a retainer, a feature such as an undercutgroove 413 that a portion of a lock inserter may secure to preventpremature release of the lock from the instrument.

An alternative form of the device is illustrated in FIGS. 12-17. Here,one or more torque stabilizers 300 in the form of an elongated key 350are partially captured within a first positioner groove 213 using atongue and groove relationship. An exploded view of this assembly isillustrated in FIG. 12 and again comprises a bone screw portion 200, atorque stabilizer portion 300, and a compressor lock portion 400.

FIG. 15 illustrates the bone screw portion which again comprises a firstpositioner in the form of a groove 213. As illustrated in FIGS. 13 and15, this grove 213 may be configured to position and capture the torquestabilizer 300 of FIG. 12. The groove 213 comprises a bottom wall 215,lateral wall 214, and a capture wall 224. The elongated key 350 torquestabilizer illustrated in FIG. 13 comprises a side wall 308, an innerwall 351, and a broad base wall 352 that is configured to slidingly movealong axis E through the groove 213 wherein the capture wall 224 of thebone screw portion 200 holds the broad base wall 352 of the torquestabilizer within the groove. The side wall 308 of the torque stabilizerportion that extends beyond the outer surface 203 of the bone screwportion 200 into the surrounding bone is a torsion stop 302 serving tointerfere with the bone to limit rotation between the bone and bonescrew portion. The distal end of this torque stabilizer key 350 maycomprise a cutter 353 shown here in the form of a sharpened edge. Theradial wall 320 may also be sharpened to ease insertion. One or moretorque stabilizer keys 350 may be used with each bone screw portion. Thebone screw portion illustrated in FIG. 15 is equipped with two firstpositioner grooves 213 to house a torque stabilizer key 350 in each.Inscribed on the outer surface 203 near the proximal end is a fastenerportion in the form of screw threads 223 which cooperate with compressorlock threads 404 (FIG. 14) during final bone fixation or threads on aninsertion tool (not shown) for bone screw insertion. In this embodimentit is preferred that the threads are on the proximal outer surface 203of the bone screw portion, however in other embodiments they could belocated on the inner cannula wall as illustrated in FIG. 3 forcooperation with a compressor such as introduced in FIGS. 10 and 11.

In this embodiment (FIG. 12), the compressor lock portion is in the formof a cap nut 450 comprising internal threading 404. As with previousembodiments, the compressor lock portion comprises a reduction surface405. Unlike prior embodiments, this reduction surface 405 is configuredto drive against the adjacent cortical bone of the femur serving asimilar function as the translation stop 315 described in otherembodiments (FIG. 6) therein causing the bone screw portion 200 to moveproximal along the surgical axis and further causing compression at thefracture site and fixation of the bone parts as the compressor lock isadvanced. The compressor lock in FIG. 14 comprises a drive 406 asdescribed in previous embodiments. The lead face 411 of the compressorreducer is configured to advance against the proximal face 325 of thetorque stabilizer portion 300 therein maintaining its capture within thefirst positioner groove. The reduction surface 405 on the compressorlock portion may comprise anti-backout features such as splines or smallteeth. In an alternative embodiment, the reduction surface 405 and thelead face 411 may be coincident.

This embodiment, the bone fixation screw in its operationalconfiguration is illustrated in FIG. 17. After insertion of the bonescrew portion at the surgical site, the key 350 is translated down thegroove 213 cutting through the surrounding bone to cause an interferencefit between the key 350 and the surrounding bone therein stabilizing thebone screw portion and the bone segments against rotation. Thecompressor lock (FIG. 14) is then advanced over the proximal end threads(FIG. 15) of the bone screw portion 200.

Illustrated in FIGS. 18-20 is another alternative embodiment. In thisembodiment the torque stabilizer 300 comprises a fixation plate portion380 extending at a pre-determined angle ‘β’ from the proximal end of thetorque stabilizer. The fixation plate 380 is preferably configured tospan inferiorly a variable distance ‘F’ as required to secure the femur.Integrated in the top surface 381 of the plate 380 is one or more bonescrew apertures 382 to house bone screws 383 used to fix portions of thefemur against the plate. The bone screw apertures 382 may becounter-bored or counter-sunk to lower the profile of the screw withinthe plate. Apertures 382 may assume a round, slotted, or other profile.The fixation plate 380 secured to the femur utilizing bone screws 383through the apertures 382 may also serve to further limit torsion andtranslation much like the translation stop 315 and the torsion stop 302.

The top surface 381 of the fixation plate 380 in FIG. 19 has acompression lock counter bore 384 to house the head of the compressorlock illustrated in FIG. 10-11. The bottom surface 385 of the fixationplate portion 380 may comprise a slightly concave surface profile toconform to the convex outer surface of the femur. Similarly, the topsurface 381 of the plate may comprise a convex profile. The top andbottom surface of the fixation plate may define a side wall 386 with apredetermined thickness ‘G’ sufficient to endure the forces placed onit.

FIG. 20 illustrates this embodiment of the bone fixation screw assemblywith fixation plate 380 in its operational configuration within thefemur. As illustrated in the figure, the fixation plate portion 380 maybe utilized to fixate an alternate fracture site within the femur.Although less preferred, the compressor lock 400 is optional in thisembodiment when adequate fixation is provided by the fixation plate 380and plate bone screws 383. In this instance the surgeon may choose torely on natural gravitational forces to compress and stabilize thefracture. FIG. 18 illustrates an exploded view of this same embodiment(plate bone screw 383 not shown).

Cortical bone is located near the surface of the bone. When possible, itis preferred that a least a portion of the translation stop 315 andtorsion stop 302 is configured to be seated within the cortical bone.For example, in FIG. 19 note that one torsional stop in the form of afin 316 is situated at the very proximal end of the torque stabilizer toengage cortical bone.

The method of stabilizing a femoral neck fracture using the discloseddevice comprises several steps generally illustrated in FIGS. 21-26. Thefracture is initially evaluated using X-ray or other imaging tocharacterize the fracture. The surgical procedure is commonly done undera general anesthetic or a spinal block. The patient is brought to theoperating room and a sterile field is created at the surgical site. Ifneeded, tension is applied to the femur to reduce the fracture andalignment is monitored using fluoroscope.

The surgeon makes an incision at the surgical site for entry to lateralfemur along surgical axis ‘C’. Using imaging, a guide wire (FIG. 21) isplaced down the anticipated surgical axis from the lateral femur,extending through the femoral neck and into the femoral head to apre-determined site.

The cannula of a bone drill (not shown) is led over the proximal end ofthe guide wire 500. The drill is sized with a boring diameter sufficientto pass the minor diameter of the bone screw portion 200. Under power orby hand, the drill creates a bore into the femur following the surgicalaxis C from the lateral femur to the femoral head. The drill is removedand a second cannulated drill with a diameter similar to the diameter ofthe enlarged portion 321 of the torque stabilizer 300 is placed over theguide wire 500. An enlarged entry bore in the femur at a depth to housethe enlarged portion of the torque stabilizer is created again by handor power drive. Alternatively, a step-cut drill comprising a smallerfirst diameter at the leading end of the drill and a larger seconddiameter at the trailing end may be used to produce the two boresconcurrently. The distal end of the enlarged bore may be flat or taperedto complement angulation of the translation stop surface 315 of thetorque stabilizer portion 300. The guide wire 500 may now be removed orpreferably left in position until the compressor lock 400 is installed.A tap instrument (cannulated if guide wire is present) is then advanceddown the surgical path to create threads for utilization by the bonescrew portion. The tap instrument (not shown) is removed. Alternatively,a bone screw portion 200 with self-tapping threads could be utilizedthereby eliminating need for the tap instrument.

The bone screw portion insertion tool (not shown) is attached to thefastener portion 221 of the bone screw 200. The tool is advanced causingthe bone screw portion to advance down the surgical axis to thepredetermined location within the femoral head (FIG. 22-23). The bonescrew portion insertion tool is then removed.

A torque stabilizer insertion tool (not shown) is mounted to the torquestabilizer at the fastener portion 323 using threads 324 if so equipped.As illustrated in FIG. 23, led by the distal torsion stops 309, thetorque stabilizer 300 is advanced by hand or impact on the tool alongthe surgical axis and positioned to capture the second positioner 301within the first positioner groove 213. The torque stabilizer 300continues advancement (FIG. 24) until the enlarged portion 321 of thetorque stabilizer is seated within the enlarged entry bore of the femur.During final advancement, the distal torsion stops 309 and the proximaltorsion stops 310 cut into the walls of the surrounding femur bone ofthe entry bore. Again, this step may require impacting the torquestabilizer insertion tool.

A compressor lock insertion tool (not shown) is fastened to the drive406 of the drive pocket 407 of the compressor lock 400. The insertiontool may comprise a retainer feature to interface with the retainerfeature of the compressor lock. In this embodiment the compressor lockretainer is in the form of an undercut 413 below the drive faces.

Leading with the distal end, the compressor lock's central axis ‘D’ isaligned with the surgical axis and rotated for advancement of thecompressor lock threads into the fastener threads of the bone screwportion (FIG. 25). Once the reduction surface on the compressor lockabuts the proximal face of the torque stabilizer, the bone screw portionwill be drawn toward the torque stabilizer thereby causing a reductionin fracture gaps, FIG. 26, and an increased level of compression betweenthe bone parts thus facilitating bone fusion. As introduced earlier,anti-backout features on the compression lock will limit potential forloosening of the fixation screw assembly. Final positioning of theimplant is checked with imaging.

The compressor lock insertion tool is removed and a wound closureroutine can be initiated.

All portions of the assembly may be manufactured of biocompatiblematerials including but not limited to commercially pure titanium andtitanium and stainless steel alloys. Although less preferred, portionsmay be manufactured from strong biocompatible polymers or ceramics.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications which fall within the true spirit and scope of the presentinvention.

We claim:
 1. A screw device for compressing and fixing together aproximal and distal bone part along a surgical axis comprising: a bonescrew portion comprising an elongate body inscribed with bone screwthreads at a leading end of an outer surface of said body; an elongatetubular torque stabilizer portion for spanning said bone parts andcomprising one or more torsion stops to engage each bone part to limitrotational movement between the bone parts and a translation stop onsaid torque stabilizer to seat against a portion of the proximal bone tolimit translation of said torque stabilizer portion along the surgicalaxis; and a compressor lock portion engaging the bone screw portion andtorque stabilizer portion to draw said bone screw portion proximallyalong the surgical axis toward said translation stop therein compressingsaid bone parts together.
 2. The device of claim 1 wherein a continuoustorsion stop is positioned on the torque stabilizer to span both boneparts.
 3. The device of claim 1 wherein one torsion stop is positionednear the proximal end of said torque stabilizer and one stop ispositioned near the distal end of the torque stabilizer.
 4. The deviceof claim 1 wherein a portion of the torsion stop defines a secondpositioner for capture by a first positioner on the bone screw portionto limit rotation between the bone screw portion and the torquestabilizer portion.
 5. The device of claim 1 wherein said compressorlock portion comprises a threaded shaft for engaging complementingthreads near the proximal end of the bone screw portion and wherein thecompressor lock portion comprises a reduction surface for engagement ofa proximal face of said torque stabilizer wherein advancing saidcompressor lock draws said bone screw portion toward said proximal face.6. The device of claim 1 wherein said torsion stop on torque stabilizerportion extends through a groove cut in the bone screw threads.
 7. Thedevice of claim 1 wherein the torque stabilizer portion comprises anenlarged portion near the proximal end defining a distal facing stopsurface.
 8. The device of claim 1 wherein the torsion stop is sharpenedto cut through bone as the torque stabilizer is advanced along thesurgical axis.
 9. A screw device for compressing and fixing together aproximal and distal bone part along a surgical axis comprising: a bonescrew portion comprising an elongate body inscribed with bone screwthreads at a leading end of an outer surface of said body and a firstpositioner; an elongate tubular torque stabilizer portion for spanningsaid bone parts and comprising one or more torsion stops to engage eachbone part to limit rotational movement between the bone parts and asecond positioner to cooperate with said first positioner on bone screwportion to limit rotation between said bone screw portion and torquestabilizer portion; and a compressor lock portion engaging the bonescrew portion and torque stabilizer portion to draw said bone screwportion proximally along the surgical axis toward said translation stoptherein compressing said bone parts together.
 10. The device of claim 9wherein a continuous torsion stop is positioned on the torque stabilizerto span both bone parts.
 11. The device of claim 9 wherein one torsionstop is positioned near the proximal end of said torque stabilizer andone stop is positioned near the distal end of the torque stabilizer. 12.The device of claim 9 wherein a portion of the torsion stop defines asecond positioner for capture by a first positioner on the bone screwportion to limit rotation between the bone screw portion and the torquestabilizer portion.
 13. The device of claim 9 wherein said compressorlock portion comprises a threaded shaft for engaging complementingthreads near the proximal end of the bone screw portion and wherein thecompressor lock portion further comprises a reduction surface forengagement of a proximal face of said torque stabilizer whereinadvancing said compressor lock draws said bone screw portion toward saidproximal face.
 14. The device of claim 9 wherein said torsion stop ontorque stabilizer portion extends through a groove cut in the bone screwthreads.
 15. The device of claim 9 wherein the torque stabilizer portioncomprises an enlarged portion near the proximal end defining a distalfacing stop surface.
 16. The device of claim 9 wherein the torsion stopis sharpened to cut through bone as the torque stabilizer is advancedalong the surgical axis.
 17. A method for compressing and fixingtogether a proximal and distal bone part along a surgical axis using ascrew device comprising the steps of: advancing a bone screw portionalong the surgical axis through the proximal bone part until seated at apredetermined location within the distal bone part; advancing a torquestabilizer portion comprising at least one external torsion stop acrossa portion of each of the proximal and distal bone parts; and rotating acompressor lock against a proximal face of said torque stabilizer todraw the bone screw portion towards said compressor lock thereincompressing and fixating proximal and distal bone parts together. 18.The method of claim 17 further comprising the steps of: aligning a firstpositioner on said bone screw portion with a second positioner on saidtorque stabilizer portion wherein said positioners cooperate to limitrotation between the bone screw portion and the torque stabilizerportion.
 19. The method of claim 17 wherein the torque stabilizerportion is advanced along the surgical axis until a translation stop onsaid torque stabilizer portion abuts a blocking portion of bone on theproximal bone portion to limit further translation.